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Abstract

Background: Adenosine Deaminase Activity (ADA) is a commonly used marker for the diagnosis of tuberculous pleural
effusion. There has been concern about its usefulness in immunocompromised patients, especially HIV positive patients
with very low CD4 counts. The objective of this study was to evaluate the sensitivity of ADA in pleural fluid in patients with
low CD4 counts.
Materials and Methods: This was a retrospective case control study. Medical files of patients with tuberculous pleuritis and
non-tuberculous pleuritis were reviewed. Clinical characteristics, CD4 cell counts in blood and biochemical markers in
pleural fluid, including ADA were recorded.
Results: One ninety seven tuberculous pleuritis and 40 non- tuberculous pleuritis patients were evaluated. Using the cut-off
value of 30 U/L, the overall sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of ADA was 94%,
95%, 19, and 0.06 respectively. The mean CD4 cell counts among TB pleuritis patients was 29 and 153 cells/microL in
patients with CD4 ,50 cells/microL and .50 cells/microL, (p,0.05) respectively. The corresponding mean ADA values for
these patients were 76 U/L and 72 U/L respectively (p.0.5). There was no correlation between ADA values and CD4 cell
counts (r =20.120, p = 0.369).
Conclusion: ADA analysis is a sensitive marker of tuberculous pleuritis even in HIV patients with very low CD4 counts in a
high TB endemic region. The ADA assay is inexpensive, rapid, and simple to perform and is of great value for the immediate
diagnosis of tuberculous pleuritis while waiting for culture result and this has a positive impact on patient outcome.